To explore a learn node to study and report on something for biology, why not the common nematode. The “What are Nematodes?” webpage at the University of Nebraska-Lincoln begins:
Nematodes are the most numerous multicellular animals on earth. A handful of soil will contain thousands of the microscopic worms, many of them parasites of insects, plants or animals. Free-living species are abundant, including nematodes that feed on bacteria, fungi, and other nematodes, yet the vast majority of species encountered are poorly understood biologically.
You can click from this explanatory page to something of an illustrated parts list for nematodes called: Interactive Diagnostic Key to Plant Parasitic, Freeliving and Predaceous Nematodes. Shown here is one of the head appendages. Bananas are a fruitful place to observe nematodes in action; excellent materials for that topic can be found on IITA Research to Nourish Africa’s Banana Nematology pages. Described there is nematode damage and symptoms caused not by “a single nematode species attacking bananas, but a complex of several species.” Nematodes can also play role in insect control. A University of Florida article explains how biological control nematodes work. The Nematode.net Genome Sequencing Center at Washington University in St. Louis is an detailed repository of nematode facts and images, the picture of the Meloidogyne hapla at the top of this post.
More learn nodes at: learnodes.com